This invention relates to a method for use in controlling the operation of the fuel system of a compression ignition internal combustion engine. The invention is particularly applicable to controlling the quantity of fuel supplied during a pilot injection which, in use, is followed by a main injection.
It has been found that the levels of combustion noise and emissions produced by a diesel engine can be reduced by supplying each cylinder with a small pilot injection prior to supplying a main injection to the cylinder. It is desirable to be able to monitor the operation of an injector in order to accurately control the quantity of fuel supplied in the pilot injection.
GB 2305727 describes a method for determining the minimum drive pulse length which must be applied to an injector to cause delivery of fuel, the method involving filtering the output of an engine mounted sound sensor to provide a signal indicative of movement of a valve needle of the injector.